1. Field of the Invention
The present invention generally relates to a memory unit which records or reproduces to-or-from a storage medium through a plurality of heads, and more particularly, to a memory unit in which a head assembly having the plurality of heads is connected with a printed circuit board having control circuits through lines.
2. Description of the Prior Art
Recently, electronic devices have been further miniaturized, and it is desired to also miniaturize a memory unit used for an external storage unit of a computer, etc. More specifically, in a magnetic disk unit which records and reproduces to-and-from a storage medium through a plurality of heads assembled in a head assembly, the number of lines connected between the head assembly and a printed circuit board having control circuits needs to be reduced.
FIG. 1 shows a schematic block diagram of an interface circuit of a conventional magnetic disk unit. A magnetic disk unit 11 shown in FIG. 1 comprises a head assembly 12 for assembling a plurality of heads, a printed circuit board 15 for controlling the head assembly 12, and a plurality of lines connecting between the head assembly 12 and the printed circuit board 15.
In the head assembly 12, differential-type heads 13-1 to 13-16 for recording and reproducing to-and-from a plurality of magnetic disks are assembled. Included in the head assembly 12 is a head IC 14, which selects one of the heads 13-1 to 13-16, and transmits-and-receives write-data and read-data. The head IC 14 is also fabricated on a flexible printed circuit board.
On the other hand, the plurality of lines between the head assembly 12 and the printed circuit board 15 comprise twelve lines which include, four head-selection signal lines 16-1 to 16-4, write-data signal lines 17-1, 17-2, read-data signal lines 18-1, 18-2, a write-gate signal line 19, a ground (GND) line 20, and two-types (12 V and 15 V) power-supply lines 21-1, 21-2.
These signal lines are constructed by flexible print circuits (FPC) or flat cables, etc., between the printed circuit board 15 and the head assembly 12.
For selecting one of the sixteen heads 13-1 to 13-16, four-bit signals are needed. The above four head-selection signal lines 16-1 to 16-4 are set for these four-bit signals. In this way, a number of the head-selection signal lines is determined by a number of bits necessary for selecting one of heads.
FIG. 2 shows a connecting configuration of the interface circuit in the conventional magnetic disk unit shown in FIG. 1. In an example shown in FIG. 2, the head assembly 12 is installed such that the sixteen heads 13-1 to 13-16 are close to magnetic disks 22-1 to 22-8. Each of these heads 13-1 to 13-16 is mounted at the top of suspension gimbals 24 connected with a carriage 23 and can be moved in a radial direction of the magnetic disks 22-1 to 22-8.
Two signal lines from each of the heads 13-1 to 13-16 are connected to associated pattern lines 26 on the flexible printed circuit board 25 through the suspension 24 and the carriage 23. Each of the pattern lines 26 on the flexible printed circuit board 25 are routed to ports of the head IC 14 mounted thereon.
On the other side of the head IC 14, each port of the head IC 14 is connected to an associated port of one side of an FPC 27. Also on the other side of the FPC 27, a connector 28a is assembled. In the FPC 27, the above mentioned twelve lines, 16-1 to 16-4, 17-1, 17-2, 18-1, 18-2, 19, the GND line 20, and the power-supply lines 21-1, 21-2, are formed by patterns 27a. Thick lines of the patterns 27a are allocated to the GND line 20 and the power-supply lines 21-1, 21-2.
On the other hand, the printed circuit board 15 for controlling and driving the magnetic disk unit 11 comprises a connector 28b, which is connected with the connector 28a, so as to connect between the printed circuit board 15 and the head assembly 12.
To miniaturize the magnetic disk unit 11, the number of lines between the printed circuit board 15 and the head assembly 12 also needs to be reduced. For this purpose, an example of reducing the number of connection lines by transmitting data in series is disclosed in Japanese Laid-open Pat. No.6-30505. In this example, a system, in which a main control unit is connected with a peripheral unit through a single data signal line and a single clock signal line, is disclosed. In this system, during one serial transmission, xe2x80x9cinformation of data-transmit/receive directionsxe2x80x9d, xe2x80x9cinformation of a data typexe2x80x9d, and xe2x80x9cinformation of dataxe2x80x9d are transmitted and received in that order.
To miniaturize the magnetic disk unit 11, the width of the FPC 27, namely the width of each pattern 27a, needs to be thinner. However, reducing the width of the pattern 27a any more causes noise due to voltage fluctuation. There is thus a problem that it is hard to miniaturize recording-and-reproducing units, such as a magnetic disk unit by thinning the width of each pattern 27a of the FPC 27.
It is an object of this invention to provide a memory unit. The size of the unit can be miniaturized by reducing the number of signal lines of the unit. Also, noise which may occur in the unit can be reduced. This permits the disadvantages described above to be eliminated.
The object described above is achieved by a memory unit having a plurality of heads performing at least one of recording or reproducing operations on a storage medium, the memory unit comprising: a first converter circuit for receiving head-selection signals as first parallel data and converting the head-selection signals to first serial data to be transmitted; a second converter circuit for receiving the first serial data from the first converter circuit and converting the first serial data to second parallel data to be transmitted; and a head control circuit for receiving the second parallel data from the second converter circuit and selectively driving the heads on the basis of the second parallel data.
In the above memory unit, the first converter circuit may be located on a printed circuit board controlling the memory unit, and the second converter circuit may be located inside a disk enclosure having the heads and the storage medium.
The object described above is also achieved by the memory unit mentioned above, wherein the memory unit further comprises a connecting circuit, including a line for the head-selection signal in the serial data form, for connecting the first converter circuit and the second converter circuit together, and the line has conductive patterns formed on a flexible material.
The object described above is also achieved by a memory unit having a plurality of heads performing at least one of recording or reproducing operations on a storage medium, the memory unit comprising: a first switching circuit for switching between transmission of record data to the heads and reception of reproduced data from the heads; and a second switching circuit for switching between reception of the record data from the first switching circuit and transmission of the reproduced data from the heads to the first switching circuit.
In the above memory unit, the first switching circuit may be located on a printed circuit board controlling the memory unit, and the second switching circuit may be located inside a disk enclosure having the heads and the storage medium.
The object described above is also achieved by the memory unit mentioned above, wherein the memory unit further comprises connecting circuit, including a line for the record data and the reproduced data, for connecting the first switching circuit and the second switching circuit together, and the line has a conductive pattern formed on a flexible material.
In the above memory units, the connecting circuit further comprises a first pattern of predetermined width and second patterns of predetermined width, the first pattern of predetermined width being wider than the second patterns of predetermined width and being formed on the flexible material.
The first pattern of predetermined width may be connected to a ground. And the first pattern of predetermined width may provide a disk enclosure bias inside the unit.
According to the memory unit, the head-selection signal is transmitted as serial data from the first converter circuit to the second converter circuit through the connecting circuit. In the second converter circuit, the head-selection signal is converted from serial data to parallel data, which is transmitted to the head control circuit to a selected one of the heads.
Therefore, the number of head-selection signal lines of the connecting circuit may be reduced, thus the whole unit size may be reduced. Further, external noise affection and interference between the signal lines may be reduced, the above makes it possible to reduce noise otherwise applied to the control data such as the head-selection signal.
According to the memory unit, the record data to the heads and the reproduced data from the heads are switched in the first and the second switching circuits. Namely, the record data and the reproduced data are time-divisionally transmitted between the first and the second switching circuits through the same line of the connecting circuit.
Therefore, the number of data-transmission lines of the connecting circuit may be reduced, thus the whole unit size may be reduced. Further, the affection of external noise and the interference between the signal lines may be reduced, so as to reduce noise applied to the record data and the reproduced data.
According to the memory unit, the wide-width patterns are formed on the flexible material for the ground line and the disk-enclosure bias line. Therefore, the impedances of the patterns may be reduced, so that the noise applied to the transmission data also may be reduced.
Other objects and further features of the present invention will be apparent from the following detailed description when read in conjunction with the accompanying drawings.